nucléoïde

A nucleoid is the irregularly shaped region within a prokaryotic cell that contains genetic material. It is not enclosed by a membrane, distinguishing it from the nucleus found in eukaryotic cells. The nucleoid is composed of DNA, typically a single, circular chromosome, along with associated proteins that help in organizing and packaging the DNA. Unlike eukaryotic chromosomes, prokaryotic chromosomes do not have histones; instead, they utilize histone-like proteins for compaction.

The genetic material in the nucleoid is responsible for all cellular functions and reproduction. While the nucleoid is the primary location of the prokaryotic chromosome, some prokaryotes may also contain smaller, circular DNA molecules called plasmids, which are located in the cytoplasm and carry genes that can confer advantageous traits, such as antibiotic resistance.

The size and structure of the nucleoid can vary depending on the species and the physiological state of the cell. DNA replication and transcription occur within the nucleoid region. The organization of the nucleoid is crucial for efficient gene expression and the proper segregation of genetic material during cell division. The term "nucleoid" is derived from "nucleus" and "-oid," meaning "resembling."